Method of manufacturing metal cages for needle bearings



Dec. 24, 1963 G. ElNAUDl 3,114,960

METHOD OF MANUFACTURING METAL CAGES FOR NEEDLE BEARINGS Filed Nov. 6, 1962 5 Sheets-Sheet l INVENTOR Giacoma Einaudi,

ATTORNEY 3,114,960 METHOD OF MANUFACTURING METAL CAGES FOR NEEDLE BEARINGS Filed Nov. 6, 1962' G. EINAUDI Dec. 24, 1963 5 Sheets-Sheet 2 INVENTOR ATTORNEY Dec. 24, 1963 1-100 OF MANUFACTURING METAL CA Dec. 24, 1963 G. ElNAUDl 3,114,960

METHOD OF MANUFACTURING METAL CAGES FOR NEEDLE BEARINGS Filed Nov. 6, 1962 5 Sheets-Sheet 5 e Q I I Y 9,4 Al/ 30&\\

INVENT OR Giacomo Einaudi ATTORNEY 3,114,960 METIIUD 9F MANUFACTURING METAL CAGES FUR NEEDLE IBEARWGS Giacomo Einaurli, Turin, Italy, assignor to RIV Ofiicine di Villar l erosa ocieta per Azioni, Turin, Italy Filed Nov. 6, 196? Ser. No. 235,773 Claims priority, application Italy Nov. 7, 1961 Claims. (Ci. 29-14%.4)

This invention relates to a method of manufacturing metal cages for needle bearings of the character wherein the end sections of the bars of the cage provide for guiding the bearing rolls parallel to each other and wherein the rolls are radially retained in the cage by, on one hand, a circumferentially enlarged intermediate section on each bar and, on the other hand, a circumferentially extending ridge or tooth on each end section of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends being radially off-set with respect of the pitch cylinder of the rolls at opposite sides of the cylinder.

The circumferentially enlarged intermediate sections of the bars are usually located within the pitch cylinder, whereas the overhanging ends of the ridges are located radially outside the cylinder; however, inverse arrangements of said sections and overhanging ends are also known and this invention equally applies to both cases.

Contrarily to conventional roller hearings, in which the bearing rollers are substantially self-steering owing to their limited length/ diameter ratio, needle bearings require precision-made cages capable of exactly guiding the rolls in their respective axial planes, i.e. in planes containing the general axis of the bearing. An imperfect parallelism (skewing) of the rolls in a needle bearing leads first to a loss in transmitted power (reduced mechanical efliciency) and then to breakage of the rolls.

In a cage of the character described hereinbefore, each of the rolls is circumferentially located and guided by opposite end sections of the pair of bars adjacent the roll. To that end, the opposite end sections on a bar in the pair exhibit towards the corresponding end sections on the other bar a pair of co-planar abutment-surfaces for the roll lying on a common chordal plane, the two chordal planes enclosing the roll therebetween being parallel and symmetrical to each other with respect of the geometrical axis of the cage and being spaced therebetween through a distance equal to the diameter of the roll (except for the required snug fit allowance).

Since the aforementioned ridges are located on said opposite end sections of the bar, and since moreover the overhanging ends on the ridges are conventionally formed by rolling or punching the ridges, said abutment-surfaces are necessarily influenced by the rolling or punching operation and result uncontrollably deformed in the finished cage. The subsequent snap-insertion of the rolls in their respective windows between the bars results therefore difficult or impossible and the rolls are subjected to skewing in use of the bearin g.

This invention provides a novel and useful manner of forming the ridges with their overhanging ends without negatively influencing the chordal abutment-surfaces on the bars.

According to this invention, in a method of manufacturing a cage of the character described hereinbefore, the step of forming said overhanging ends on a ridge consists of axially squeezing the end zones at least of the ridge thereby to cause the ridge metal to plastically flow in circumferentially opposite directions to form said overhanging ends.

It is to be understood that the terms such as axial, radial, chordal and circumferential are to be referred to the general geometry of the cage.

States Patent 0 "ice According to a preferred embodiment of the invention, the surfaces between which the ridge is to be axially squeezed are inclined towards each other and converge above the ridge, thereby to hinder a substantial (or any) flow of metal radially of the cage.

Further details and characteristic features of this invention will be described with reference to the accompanying drawings, given by way of example, wherein:

FIGURE 1 is a schematical cross-sectional view showing a cage blank and a corresponding machining-tool profile;

FIGURE 2 is a fnagmentary perspective view of the blank of FIGURE 1;

FIGURE 3 is a schematic perspective part-view of a ridge-region on a cage bar with a pair of squeezing tools;

FIGURE 4 is a view similar to that of FIGURE 3 showing mutually concave squeezing surfaces;

FIGURE 5 is a perspective partview of a one-piece tool for simultaneously squeezing the ridges on opposite end sections of a bar;

FIGURE 6 is a cross-sectional part-view on line VI- VI of FIGURE 5, showing a practical manner of obtaining concave squeezing surfaces on the one-piece tool;

FIGURES 7 and 8 are cross-sectional part-views of a ridge and tool in two different stages of the squeezing operation;

FIGURES 9 and 10 are cross-sectional part-views on :lines IX--IX and X-X of FIGURES 7 and 8, respec tively;

FIGURE 11 is a cross-sectional axial part-view showing a one-piece tool in operative position on a bar of the blank shown in FIGURES 1 and 2;

FIGURE 12 is a cross-sectional view on line XII-XII of FIGURE 7;

FIGURE 13 is a fragmentary plan view of a finished cage having a roll snap-fitted between a pair of bars;

FIGURE 14 is a cross-sectional view on line XIV-XIV of FIGURE 13.

For performing the instant invention a cage-blank is required having a circumvferentially directed ridge on each end section of each bar. The manner of forming such a blank is not critical, provided the chordal abutmentsurfaces for the rolls are precisely defined at the opposite end sections of the bars.

The apparently best way experimentally ascertained for obtaining such a blank consists in turning the inner and outer surfaces of a metal bushing to a desired profile, including a circumferential continuous ridge on each end section of the bushing, and then radially punching the latter by means of punching-coining tool thereby to obtain a circumferential series of precision-sized windows for the rolls.

Thus, the blank 2% shown on FIGURES 1 and 2 comprises opposite end crowns 21, 22, having integral therewith axially directed bars .23 which define therebetween windows 24 for the rolls 25. In the example shown, the inner surface of the blank is cylindrical of a constant diameter, whereas the outer surface has been machined on a lathe by means of a profiled single cutter 26 by radially feeding the cutter against the workpiece. In this manner the outer surface of the workpiece has been sirnu1- taneously machined to an exact profile, the latter including an axially intermediate section 27 which is located on a diameter smaller than the mean diameter of the blank, or, better said, is radially off-set with respect of the pitch cylinder 28 (see FIG. 14) of the rolls to the inside of said cylinder. The blank profile also comprises a circumferentially directed ridge 30 on each end section 29 of each of the bars, the crest-line or crest-surface of the ridge being substantially flush with the cylindrical surface enveloping the blank. The crosssectional shape of the ridges shown is slightly trapezoidal due to machining requirements (successful penetration and easy withdrawal of the cutter 26); thus, the flanks 359a of each ridge 30 (FIG. 12) are inclined through an angle 6 to a plane 31 perpendicular to the cage axis, the angle 3 usually not exceeding about Alternatively, the cross-sectional shape of the ridge can be rectangular, if desired, or can exhibit a rectangular base-portion followed by a trapezoidal apex-portion. Trapezoidal shape is also advantageous in that a definite deforming specific pressure applied to the apex-portion of the ridge will produce a lower non-deforming specific pressure at the root of the ridge according to the ratio of the respective areas.

The radially performed punching results in windows 24 having mutually parallel longitudinal wall surfaces and mutually parallel front wall surfaces. The latter are indicated by 32 in the drawing, whereas each of the longitudinal wall surfaces is a stepped surface comprising a pair of co-planar end portions 33 and an intermediate portion 34 projecting out of the plane of the end portions 33 towards the opposite longitudinal wall surface. In other words, the intermediate section 27 of each bar 23 is somewhat enlarged in circumferential direction with respect of the end sections 29 of the bar. The width of the windows 24 at their end sections is substantially equal to the diameter of the rolls 25 as stated hereinbefore, whereas the mutually opposite intermediate surface portions 34 in each window are spaced from each other through an extent smaller than the diameter of the rolls. Thus, the surface portions 33': provide the aforementioned chordal abutment-surfaces for guiding the rolls each on its proper plane extending through the axis of the cage, and the enlarged intermediate sections of the bars provide radially inner retaining means for the rolls. It will be also understood that, owing to punching, the opposite end surfaces of each ridge 3d are flush with their corresponding chordal surfaces 33, so that the ends of the ridges do not project into the windows 24.

According to the scheme shown in FIG. 3, wherein a bar 23 with one of its ridges St is shown, the apex zone of the ridge is positioned between a pair of squeezing tools 3-6, 37, arranged for being pressed towards each other in axial direction. The squeezing surfaces 36a, 37a, of the tools are planar and form a sort of roof above the ridge by being inclined towards each other so as to initially engage the apex edges Ella, 30b, only, of the ridge 3t Thus, on axially pressing the tools towards each other, and extremely high specific pressure is applied to the apex zone of the ridge, the pressure having a limited radial component directed towards the root of the ridge. Such a component, when distributed over the cross-sectional area of the root, is insignificant and uncapable of producing any permanent deformation, while, on the contrary, the apex zone of the ridge is progressively squeezed by the high specific pressures applied thereto. A radially outward plastic flow of metal is satisfactorily prevented by said radial component of pressure, so that the metal mainly flows in circumferentially opposite directions lengthwise of the gap between the tools to provide overhanging ends on the ridge. Since, as will be readily realized by an expert, a protrusion of a ridge end by no more than 0.2 mm. into the window is sufficient for retaining a roll of 3 mm. diameter, the necessary plastic how of metal is relatively limited as compared with the volume of the ridge.

The flow of metal originating from a centrally located zone of the ridge length contributes relatively little to the formation of the overhanging ends; thus, according to a preferred embodiment of this invention, the squeezing pressure is mainly applied to the end zones of the ridge. To that effect, the tools 136, 137, shown in FIG. 4 exhibit towards each other and towards the ridge 30 a concave surface 136a, 137a, respectively. In such an embodiment, the four corners 30' of the ridge are first engaged by the squeezing surfaces and are plastically deformed to give rise to horn-like projections extending in circumferentially opposite directions, as will be better seen hereinafter.

Since the tools such as 36, 37, and 136, 137, pinch the ridge therebetwecn, such tools could be formed on the two jaws of a pliers-like device. However, such a device would result relatively complex and delicate; so, it has been found that the squeezing surfaces should not necessarily be displaceable towards each other. According to the most advantageous embodiment of this invenion shown in FIG. 5, a sort of coining tool it) is employed, having an elongated planar face 41 in which transverse grooves 42, 43, are formed at a mutual distance equal to that of the two ridges 3t) on a bar of the cage to be manufactured. Each of said grooves has a V-shaped ross-sectional profile and is easily obtained by means of a rotary grinding or milling tool schematically denoted by 44 in FIG. 6, the feed of which is directed perpendicularly to the surface 41 and the shape of which is biconical; such tools are frequently used to cut V-grooves when their feed is directed parallel to the surface being machined. The grinding or milling tool diameter is smaller than the outer diameter of the cage, so that the curvature of the bottom 45 of each of the grooves 42, 43, is greater than the curvature of the crest 46 (FIG. 9) of the ridge 39. In this manner, owing to the bi-conical shape of the grinding or milling tool, the flanks 47, 48, of each groove will result concave towards the ridge (FIG. 5).

I11 operation, the cage blank 2% (see FIG. 11) is fitted on a suitable mandrel 5%, whereby a bar such as 23 is firmly supported radially by the mandrel, and the tool at is radially fed to engage by its grooves 42, 43, the two ridges 363 on the bar 23. The deforming axially-directed pressure is applied by the groove flanks 4'7, 48 (FIG. 7) at first to the four corners 3d of the ridge 3% as in the case of FIG. 4. As the tool advances, the ridge 3t wedges into the groove whereby the opposite end Zones of the ridge start plastically deforming and the ridge metal plastically flows in circumferentially opposite directions (FIGS. 8 and 10). Back-low of metal is prevented both by the limited radial component of the applied pressure and by the ridge-to-tool contact progressively propagating towards the central zone of the ridge length. As a result, the ridge is squeezed in axial direction and overhanging ends are formed on the ridge taking a form of horn-like projections 51. Excellent results are obtained with wedge semi-angles 0c of the grooves 42, 43 (FIG. 12) comprised between about 10 and 35; greater angles, up to about 40-45 may be adopted, provided the interengaging tool and ridge surfaces are adequately lubricated to reduce friction. Moreover, the angles a and ,8 should advantageously be adapted to each other to obtain a positive differential angle 7 amounting to at least 4-5 to thereby keep the high specific squeezing pressure possibly way of the root of the ridge, hence away of the chordal abutment-surface 33.

FIGURES 13 and 14 show a general aspect of the ridges 30 in a finished cage, a roll 25 having been snapinserted between a pair of bars 23. It will be seen that the hornlike projections 51 extending from the ridges 3G in circumferentially opposite directions efficiently prevent an outward escape of the roll 25, the chordal abutment-surfaces 33 being left undistorted. As compared with retaining ridges obtained by known methods, the horn-like ends of the instant ridges have a specific advantage residing in that they easily round-01f to a little extent when an excess resistance is encountered in snapfitting a roll therebetween, so that incidental permanent deformation of the bars on assembly of the bearing is avoided.

What I claim is:

1. In a method of manufacturing a metal cage for a needle bearing of the character wherein opposite end sections of the bars provide for guiding the rolls parallel to each other and wherein radially effective retaining means for the rolls are integrally formed on each of the bars comprising a circumferentially enlarged intermedate section of the bar and a circumferentially extending ridge on each of said end sections of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends or" the ridge being radially oil-set with respect of the pitch cylinder of the rolls at opposite sides of the cylinder; the step of forming said overhanging ends on a ridge by axially squeezing the opposite end Zones at least of a ridge having non-overhanging ends to thereby cause the ridge metal to plastically flow in circumterentially opposite directions to form said overhanging ends.

2. In a method of manufacturing a metal cage for a needle bearing of the character wherein opposite end .ections of the bars provide for guiding the rolls parallel to each other and wherein radially effective retaining means for the rolls are integrally formed on each oi the bars comprising a circumferentially enlarged intermediate section of the bar and a cireumierentially extending ridge on each of said end sections of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends of the ridge being radially oilset with respect of the pitch cylinder of the rolls at opposite sides of the cylinder; the step of forming said overhanging ends on a ridge by axially squeezing the opposite end zones at least of a ridge having non-overhanging ends between a pair of tool surfaces converging above the ridge to thereby cause the ridge metal to plastically flow in circumferentially opposite directions to form said overhanging ends.

3. In a method of manufacturing a metal cage for a needle bearing of the character wherein opposite end sections of the bars provide for guiding the rolls parallel to each other and wherein radially effective retaining means for the rolls are integrally formed on each of the bars comprising a circumferentially enlarged intermediate section of the bar and a circumferentially extending ridge on each of said end sections of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends of the ridge being radially off-set with respect of the pitch cylinder of the rolls at opposite sides of the cylinder, the step of forming said overhanging ends on a ridge by axially squeezing the opposite end zones at least of a ridge having non-overhanging ends between a pair of mutually concave tool surfaces converging above the ridge to thereby causing the metal to plastically flow in circumferentiaily opposite directions to form said overhanging ends.

4. In a method of manufacturing a metal cage for a needle bearing of the character wherein opposite end sections of the bars provide for guiding the rolls parallel to each other and wherein radially effective retaining means for the rolls are integrally formed on each of the bars comprising a circumferentially enlarged intermediate section of the bar and a circumicrentially extending ridge on each of said end sections of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends of the ridge being radially oiset with respect of the pitch cylinder of the rolls at opposite sides of the cylinder; the step of forming said overhanging ends on a ridge by radially wedging a ridge having non-overhanging ends between a pair of mutually fixed tool surfaces converging above the ridge to thereby axially sequceze the ridge between said surfaces and cause the ridge metal to plastically flow in circumferentially opposite directions to form said overhangin ends.

5. In a method of manufacturing a metal cage for a needle bearing of the character wherein opposite end sections of the bars provide for guiding the rolls parallel to each other and wherein radially effective retaining means for the rolls are inte rally formed on each of the bars comprising a circumferentially enlarged intermediate section of the bar and a circumferentially extending ridge on each of said end sections of the bar having overhanging ends, said intermediate section of the bar and said overhanging ends of the ridge being radially off-set with respect of the pitch cylinder of the rolls at opposite sides of the cylinder; the step of forming said overhanging ends on a ridge by radially wedging a ridge having non overhanging ends between a pair of mutually concave tool surfaces converging above the ridge to thereby axially squeeze the ridge between said surfaces and cause the ridge metal to plastically flow in circumferentially opposite directions to form said overhanging ends.

References (Cited in the file of this patent UNITED STATES PATENTS 

1. IN A METHOD OF MANUFACTURING A METAL CAGE FOR A NEEDLE BEARING OF THE CHARACTER WHEREIN OPPOSITE END SECTIONS OF THE BARS PROVIDE FOR GUIDING THE ROLLS PARALLEL TO EACH OTHER AND WHEREIN RADIALLY EFFECTIVE RETAINING MEANS FOR THE ROLLS ARE INTEGRALLY FORMED ON EACH OF THE BARS COMPRISING A CIRCUMFERENTIALLY ENLARGED INTERMEDIATE SECTION OF THE BAR AND A CIRCUMFERENTIALLY EXTENDING RIDGE ON EACH OF SAID END SECTIONS OF THE BAR HAVING OVERHANGING ENDS, SAID INTERMEDIATE SECTION OF THE BAR AND SAID OVERHANGING ENDS OF THE RIDGE BEING RADIALLY OFF-SET WITH RESPECT TO THE PITCH CYLINDER OF THE ROLLS AT OPPOSITE SIDES OF THE CYLINDER; THE STEP OF FORMING SAID OVERHANGING ENDS ON A RIDGE BY AXIALLY SQUEEZING THE OPPOSITE END ZONES AT LEAST OF A RIDGE HAVING NON-OVERHANGING ENDS TO THEREBY CAUSE THE RIDGE METAL TO PLASTICALLY FLOW IN CIRCUMFERENTIALLY OPPOSITE DIRECTIONS TO FORM SAID OVERHANGING ENDS. 